The present invention relates to film duplicators and particularly to duplicators for making one or more copies of a microfiche master.
The prior art discloses a variety of film and microfiche duplicators. Generally speaking, such duplicators provide that the master be positioned at a transfer station and that copy film be incrementally advanced past the transfer station for "contact printing." As used herein "contact printing" means that the copy film is brought into intimate contact with the master by biasing the two against each other and to thereafter direct light past the master onto the copy film to reproduce the master images on the copy film. After each copy is made the copy film is incrementally advanced. Exposed copy film sections are taken up on an exposed film reel. After the desired number of copies has been made the exposed copy film is developed and severed into individual copy film sections each of which is a duplicate of the master at the transfer station.
A drawback of such duplicators is the fact that the copies are only available after the exposed film roll is developed and fixed. This may involve substantial time delays which in many applications are undesirable or unacceptable.
To overcome this problem it has been suggested to sever each film section as soon as it has been exposed. This is normally accomplished by grasping an end of the copy film and advancing it after completion of a contact printing step. This approach involves a waste of expensive film and is therefore economically unattractive since an unused length of copy film at the free end of the film is necessary to enable the grasping of the film. To accommodate the necessary high film advancing speeds, this approach was nevertheless generally adhered to.
The small image size on microfiche and the required high image resolution makes it further necessary that light sources which provide a high light density be used. In the past, the desired light intensities were obtained from metal halite lamps. Such lamps provide the desired light intensity but must be turned on as much as one half-hour before they reach their peak intensity. Furthermore, they must remain turned on as long as copies are made, or might be made, since they require the long warm-up period each time they are turned off. This wastes substantial amounts of energy and is relatively expensive. Moreover, the lamps create large amounts of heat. They therefore require complicated cooling devices, fans, and the like, to keep the duplicator within an acceptable operating temperature range.